1. Field of the Invention
The present invention relates to a capacitive touch system and a method of operating a capacitive touch system, and particularly to a capacitive touch system and a method of operating a capacitive touch system that can utilize the Wheatstone bridge principle to quickly detect whether the touch panel is touched.
2. Description of the Prior Art
Please refer to FIG. 1, FIG. 2, and FIG. 3. FIG. 1 is a diagram illustrating a touch panel 100, FIG. 2 is a diagram illustrating a detection circuit 200 of the touch panel 100, and FIG. 3 is a diagram illustrating the detection circuit 200 detecting the touch panel 100 touched by a finger and the touch panel 100 not touched by the finger. As shown in FIG. 1, the touch panel 100 includes a plurality of sensing lines XS1-XSN along an X axis and a plurality of sensing lines YS1-YSM along a Y axis, where each sensing line is coupled to a plurality of sensing units, and N, M are integers. As shown in FIG. 2, a current source 202 of the detection circuit 200 can charge the plurality of sensing lines XS1-XSN and the plurality of sensing lines YS1-YSM in turn according to a predetermined timing. Therefore, the detection circuit 200 can detect a location of a touch point on the touch panel 100 through capacitance variation of a parasitic capacitor SC of two adjacent sensing units of the touch panel 100. As shown in FIG. 2 and FIG. 3, when the touch panel 100 is not touched by the finger, a period for a parasitic capacitor SC between two adjacent sensing units of the plurality of sensing lines XS1-XSN (or the plurality of sensing lines YS1-YSM) being charged to a reference voltage VREF is T1. That is to say, when the parasitic capacitor SC is charged to the reference voltage VREF, a comparator 204 generates a reset signal RS to a counter 206 and a switch 208. Meanwhile, the counter 206 can record the period T1 according to a clock CLK and the reset signal RS of the counter 206 and reset a count of the counter 206 at the period T1, and the switch 208 can reset a potential stored in the parasitic capacitor SC according to the reset signal RS at the period T1 and make an output of the comparator 204 back to an initial state. As shown in FIG. 2 and FIG. 3, when the touch panel 100 is touched by the finger, a period for a parasitic capacitor SC′ (because the parasitic capacitor SC′ is equal to the parasitic capacitor SC being in parallel with a parasitic capacitor caused by the finger, the parasitic capacitor SC′ is greater than the parasitic capacitor SC) between two adjacent sensing units of the plurality of sensing lines XS1-XSN (or the plurality of sensing lines YS1-YSM) touched by the finger being charged to the reference voltage VREF is T2, where the period T2 is greater than the period T1. Therefore, the touch panel 100 can repeat the above mentioned process to detect a touch point of the touch panel 100 through a timing controller. However, the above mentioned detection method can have a slower detection speed, not realize a multi-touch function easily, and be influenced by noise easily.